Title

Grasping and Lifting Different Materials

Authors

Gavin Buckingham, The University of Western OntarioFollow
Jonathan S. Cant, The University of Western Ontario
Melvyn A. Goodale, The University of Western OntarioFollow

Document Type

Presentation

Publication Date

2009

Abstract

The material from which an object is made can determine how heavy it feels (Seashore, 1899). Interestingly, a metal block that has been adjusted to have the same size and mass as a polystyrene block will feel lighter than the polystyrene block. We recently showed that participants experiencing this material-weight illusion’ (MWI) do not apply forces that match their perceptual experience of heaviness ‐ just like in the size‐weight illusion ( Flanagan & Beltzner, 2000).

Our previous study showed that forces on early trials were scaled to each participant’s expectations of how much a particular block should weigh ‐ excessive force was applied to the metal block and insufficient force was applied to the polystyrene block. Forces on later trials scaled to the real weight of each block ‐ identical levels of force were applied to all the blocks. MWI persisted throughout – the polystyrene block felt the heaviest and the metal block felt the lightest.We followed this finding up with two experiments:

Experiment 1 – different weight, different material: We adjusted the weight of each block slightly in the opposite direction to the illusion, predicting that we would find opposing perceptual and motor responses (e.g., Grandy & Westwood, 2006).

Experiment 2 – different weight, same material: We also removed the visual differences between the blocks, keeping the slight difference in weight, predicting that the dissociation between perception and action would disappear.

Notes

A poster presentation at the Centre for Vision Research (CVR) Meeting held in Toronto, ON in 2009